Light diffusing thermoplastic tube to encircle an elongated lighting element



May B951 c. E. SLAUGHTER LIGHT DIFFUSING THERMOPLASTIC TUBE T0 ENCIRCLE AN ELONGATED LIGHTING ELEMENT 2 Sheets-Sheet 1 Filed May 4, 1945 17/7' OAIVE K y 1951 c E SLAUGHTER 2,551,710

LIGHT DIFFUSING TH ERMOPLASTIC TUBE TO ENCIRCLE AN ELONGATED LIGHTING ELEMENT Filed May 4, 1945 2 Sheegs-Sheet 2 r i a INVENTOR. Charles ESIaug/zkr BY Patented May 8, 1951 LIGHT DIFFUSING THERMOPLASTIC TUBE TO ENCIRCLE AN ELONGATED LIGHTING ELEMENT Charles E. Slaughter, New Canaan, Conn, assignor to Extruded Plastics, Inc., Norwalk, 'Conn., a corporation of Connecticut Application May 4, 1945, Serial No. 592,035

8 Claims.

This invention relates to splined tubing, to articles utilizing such splined tubing, and to methods of making such tubing and articles.

Among the objects of this invention is the production of splined tubing by simple and economical methods.

Further objects include splined tubing of novel character and utility.

Still further objects include articles produced from or with such splined tubing.

Still further objects and advantages of the present invention will appear from the more detailed description set forth below, it being understood that such more detailed description is given by way of illustration, and not as limiting, since various changes therein may be made by those skilled in the art, without departing from the scope and spirit of the invention.

In accordance with that more detailed description, there is shown in the accompanying drawing, in

Figure 1, a transverse section through tubing made in accordance with this invention; in

Figure 2, a plan view of an article using the tubing of Figure 1; in

Figure 3, a transverse section through a modifled form of tubing; in

Figure 4, a transverse section through a further modification of tubing; in

Figure 5, a transverse section through a still further modification of tubing; in

Figure 6, a transverse section through another type of tubing; in

Figure '7, a vertical section through an article made with the tubing of Figure 6; in

Figure 8, a transverse section through another form of tubing; in

Figure 9, a plan view of a discrete length of the tubing of Figure 8; in

Figure 10, a transverse section through tubing of modified character; in

Figure 11, a container made of tubing of Figure 10; in

Figure 12, a lighting fixture of tubing of Figvure 10; in

Figure 13, a section through a further modified form of tubing; and in Figure 14, a section through another modification of tubing.

In accordance with the present invention, tu ing is produced having a number of splines extending a substantial distance from the inner wall of the tubing and internally thereof, the splines and the tubing being integral. Such tubing is desirably produced by extrusion in the form of continuous tubing from which discrete lengths may be cut as desired. While it may be made of any desired material, it is preferably of thermoplastic composition which has particular value and utility for the purposes of the present invention as will more particularly appear below.

As such thermoplastic material there is desirably used a synthetic resinous material including for example: cellulose derivatives such as the esters and ethers, particularly cellulose acetate, cellulose nitrate, cellulose acetate butyrate, ethyl cellulose, benzyl cellulose, etc.; vinyl polymers and copolymers including polymerized Vinyl acetate, polymerized vinylidene chloride, and copolymers of vinyl chloride and vinyl acetate; polymerized styrene; methacrylate and methyl methacrylate res-ins; polyethylene; nylon type resins; etc. Such plastic materials particularly lend themselves to use in any desired color or configuration which as will be seen below are specifically important for certain purposes hereinafter set forth.

Further, for certain purposes, there may be used oil-filled material such as oil-filled ethyl cellulose. Such oil-filled material may be produced by milling a desired oil into the synthetic resin.

The splined tubing produced in accordance with the present invention, may take a variety of structural forms or modifications depending on the particular use to which such tubing is to be put. Thus the splines may be radial or nonradial; that is, they may lie along radii of the circle of tubing that is circular in cross-section; or they may lie along the line of chords of such circle when the tubing is circular in cross-section. In the first case they may be described as at right angles to the tangents at the circle, while in the second case they would be at other than a right angle to such tangents. When nonright angular splines are used in diffusion elements for fluorescent lighting fixtures as set forth below as well as for other purposes, the splines should extend inwardly for a distance sufiicient to prevent a direct line of vision from the outside of the tubing to its center if maximum diffusion is to be obtained. In such cases, the length of the spline and the angle of the spline may be coordinated to obtain this result.

The cross-section of the tubing may take any desired configuration and may be circular, oval or elliptical, square, oblong, hexagonal or otherwise polygonal, or a combination of such shapes may be used as for example a combination of circular or oval walls with intermediate square or hexagonal walls. However for purposes of illustration the invention will be described by means of the tubing that is circular in crosssection.

One of the principal uses of tubing made in accordance with the present invention is in conditioning the light from fluorescent lighting elements. Light from such sources is generally too strong for comfortable use so that some means for diffusing the light is essential. However such. diffusion means should not reduce the light obtained to a point where it is dimmed too greatly. There has been diificulty in the prior art in obtaining a balance of diffusion with retention of suificient lighting. Tubing produced in accordance with the present invention has proved to solve this problem particularly when extruded thermoplastic tubing is employed. The balance of diffusion between light diifusion and transmission is obtained by adjustment of the position of the splines, of the thickness of tubing wall and spline thickness, of the nature of the thermoplastic, and of the dye or color used in or with the thermoplastic all as more fully explained below. Since the extruded thermoplastic materials have a high reflecting value, light from the tube will not be materially reduced in value except for the absorption of light by the outer wall of the tube. This wall thickness can be kept quite low, for example around .030" to .050 so that absorption may be about 10% in all. It is apparent that adjustment of wall thickness and other factors mentioned above may be utilized to control such absorption or diffusion.

In all cases whether the splines are radial or non-radial, but particularly when radial splines are used, the efiiciency of light diffusion may be materially increased by modifying the nature of the inner wall surfaces of the tubing as between the splines.

For such purposes the inner walls of the tubing between the radial splines for example, may be given a faceted structure as for example by forming ribs longitudinally on the inner walls of the tubing during the extrusion process. Such ribs may be angular in cross-section and the angles may for example be 60 or 90. The use of such faceting ribs enables the number of splines to be reduced in number. While any number of splines may be used, by iaceting the inner walls of the tubing as described above, the splines may be six in number regularly positioned at an equal distance from each other with faceting between them. Angular faceting is preferable for light diffusion purposes although other configurations such as arcuate may be used. Where splines and faceting are employed, the splines may serve primarily to hold the lighting element in position, and the length of the splines for that purpose will be sufficient to position the lighting element centrally within the tubing and to provide air circulation to keep the heat, usually quite low, away from the surface of the tube to prevent or reduce materially, the possibility of crazing, depending on the particular plastic employed. However, even if the sharp edges of the splines craze over a period of time, the area is so small that it does not interfere with efiicient operation. The splines acting in this way also keep the heat away from the facets so that there is little disturbance of the angle of the facets over long periods of time, which is important in retaining the light diiiusing properties of the facets.

The longitudinal ribs which serve as facets may be used over the entire area of the inner walls of the tubing between the splines, or may cover only a part of such area. For example, only the lower portions of the tubing when used for light diiiusion may carry such faceting, and the latter may then cover one-half or two thirds of the internal area of the tubing, for example. The unfaceted area may be used as the light diffusing area at the upper portion of the lighting fixture so that less absorption of light is obtained at that portion in line with the reflector of the lighting assembly.

Tubing used for the purposes of the present invention is very desirably kept within rather close tolerances, as for example a tolerance of about one-half of one percent based on the diameter of the tubing. In this way it is possible to maize structures of exacting dimension and controlled efhciency. It is not possible with glass structures to maintain tolerances even closely approximating those set forth above for the thermoplastic tubes.

Another expedient that may be utilized for control of light diffusion, transmission, or absorption is dyeing of the thermoplastic. While a dyed thermoplastic in which the dye or pigment is disseminated within the thermoplastic, may be used, it is preferable at least for light diffusing elements to use thermoplastic which has been dyed more or less on the surfaces only, by application of dyes which take with the particular thermoplastic being used.

For example, liquid dyes or dye solutions may be applied to the acetates, methacrylates, etc.. by pouring the dye through the tubing sufiioient contact being maintained to secure the dyeing eflect desired. In this way it is possible to dye the inner walls of the tubing, the splines, and the faceting faces. By this method there will be three dyed faces so that direct vision from the outside will see three times more color effect than the actual depth of color. At the same time, however, the light source through reflection will pass through one dyed surface only thus giving a far higher degree of light transmission. In such internal dyeing, since the color may be only approximately .001 in thickness, there will be higher light transmission as compared with tubing made from colored resin.

The dyed products are not only important from the light transmitting, absorbing, and reflecting standpoint, but also may be used for their decorative effect. Further, by the use of wash dyeing as set forth above, it is possible to dye in between the splines without dyeing the splines themselves. And if desired, one-half of the area of the tubing may be dyed one color, while the other portion is left uncolored, or colored with a dye different from that of the first mentioned dye. So that where color is used for decorative effect, unique results are obtained, there is reduction in loss of light efliciency, and at the same time an eilective shaded color effect is secured.

Referring now to the structures as shown in the drawing as illustrative of the present inventicn, in Figure 1 there is shown in cross-section, extruded tubing I having splines 2, 2 extending along radial lines internally from the inner walls of the tubing for a distance to support a lighting element which may be a fluorescent tube, shown in cross-section at 3. The splines thus serve to position the lighting element within the tube I, also to provide spaces 4, 4 for ventilation and heat dissipation, but also to provide light diffusion that reduces glare from the lighting fixture. A plan view of this structure using a disit to the center. This materially i1 crete length of such tubing about the lighting element is shown in Figure '2.

In Figure 3, the modification shows a crosssection through tubing similar to that of Figure 1 having; tubing wall 5 with splines 6, a, while four of the six spaces between the splines are shown at .l, l in which areas the inner walls of the tubing 5 are provided with faceting which as explained above may take the form shown of angular ribs or serrations running longitudinally of the tubing and produced at the time of extrusion. In the form shown in this figure, the facets are at an angle of approximately 60".

In Figure 4, the modification is similar to that shown in Figure 3 except that the faceting is produced in all of the areas between the splines. As shown the tube 8 has splines 9, while 69 angle faceting is shown at H3, 5!! in all of the spaces between the splines 9.

In the modification shown in Figure 5, the splines are non-radial. The tubing 5 l is integral with a multiplicity of splines l2, l2 1" along chords of the cross-section circular configuration. These splineextend inwardly a sufficient distance to support the lighting element l3 shown in cross-section, and W1 h may for example be a fluorescent lighting tune, and the length of the splines l2, i2 is such the outer ends i l, it of the splines overlap the inner ends l 5, I5 of the splines so that there is no direct line of vision from the outside of the tube i 2 through proves the lighting effect obtained without glare. However, Figure 5 represents a less preferred form of the device than Figures 1 to i in view f the greater 1 amount of resin or plastic required making the structure. In any of these devices, if desired, some of the splines can be omitted still retaining a suflicient number to center th lighting element, and the tubing used in such way that the portion without splines faces the reflector portion of the lighting assembly. And in any of the modifications as described alcove, dyed plastic may be used preferably of the wash dyed type as explained above, either with the entire internal area of the tubing, splines, and facet dyed, or a portion thereof dyed,-or with portions contrastingly dyed, all as explained above. If desired, the outer face of the tubing may also be dyed, or fluorescent material may be applied to the inner or outer surfaces of the tubing or incorporated into the plastic.

The tubing as described above, has been pre sented primarily from its use as diffusion lighting elements but such tubing has many other utilities. Thus it may be used in the rm of discrete lengths as containers, if the splines are placed near enough together and are of Sufi cient length, compartments are formed between the splines for reception of articles. In such cases, caps may be provided as explained below connection with Figure '7 to act as closures. Articles such as drills, pencil leads, etc. may be packaged in this way. Where metal articles such as drills, taps, etc. are packaged, the plastic may be oil-filled as explained. above to act a rust retardant or preventative.

However, when such extruded tubing is to be used as a packaging medium, it is preferred to extrude the tubing with a central suppor' member which may be in the of a tube rod. As shown in Figures 6 and '7, a tube having the cross-sectional configuration shown in Figure 6 may be provided in which the tubing it carries radial splines ll, ll and a centrally positionecl supporting tube 58, all of the described elements being int gral and formed simultaneously during extrusion. The number of splines may vary as desired to produce compartments or chambers ii), is for reception of elongated articles. Simple closures may be provided in the form of caps 20, 20 of a diameter equal to that of the tubing 56, the caps having lugs 2|, 2i integral with the caps, and of a diameter to fit snugly within the tubing l8 to hold them securely.

Splined tubing as shown for example in Figure 1 may also be used very effectively as a packaging medium. For example, any desired article may be carried within a discrete length of such tubing in a manner similar to that shown in Figure 2 except that the tubing in such case is made long enough to cover the article. More desirably, tubing of this character used for packaging may be made from one of the rubber-like resins, as for instance, a heavily plasticized vinyl resin and employed to protect fragile articles in transportation. Thus radio tubes may be packaged in this way as well as many other articles, for example, ampules containing medicaments or pharmaceutical preparations. The splines fitting snugly around the radio tube, ampule, etc, and being quite flexible, serve as a most efficient shock absorber.

Structures of the character shown in Figures 6 and 7 be made of any desired size, i. e., width length. Small size tubing thus produced may be used for a variety of purposes as a container for small elements and also as a filler for viscous liquids. Such a structure is shown in Figures 8 and 9. As shown in cross-section in Figure -8 tubing that may be of small outside diameter such as three-eighths inch is produced which may have an external fluted surface as shown at 2'2, and has internal splines 23, 23 joined at the center of the tubing to the central element 2 which in this case may be a rod like element, all of the par-ts being integral and formed during extrusion, thus forming compartments 5, 25. A discrete length of such tubing as shown in Figure 9 may be used as a filler for viscous liquids which are held within the filler compartments by capillarity until used. The

h of such tubing 26 may be made as desired. If desired, caps may be placed at each end of the filler, and such fillers sold as articles of commerce. A variety of viscous liquids, of any desired color, etc, may thus be supplied eliminating the necessity for bottles, etc. Plastics repellent to the viscous liquid may be used for such fillers if desired.

When the faceted tubing is used for containers, it may be produced without the splines as shown in section. in Figure ii). In this case, the extruded tubing 2'! carries the internal longitudinal seriations or ribs 28 which serve as faceting. Generally, as shown for such cases the faceting will extend around the entire perimeter of the tubing although it may be placed only on a part thereof as indicated in Figure 3. In Figure 11, there is illustrated a container made from the tubing of Figure 10, in which a discrete length 23 of such tubing carrying the internal faceting 28 is provided with caps to form a very attractive container due to the light effects proby the faceting. The plastic may be dyed in any color, as may the caps, either in the same or a contrasting color, by internal dyes or by wash dyeing as explained above.

The internally faceted tubing as shown in Figure 10 is not limited in use to containers but may be used for a variety of other purposes including light diffusion for fluorescent lighting elements as explained above for the tubing of Figure 1 and illustrated in Figure 2. In this case where the non-splined tubing is used, some other means for supporting the faceted tubing about the lighting element is necessary. This may be in any desired way as for example by discs of a size to fit between the lighting element and the tubing. As shown in Figure 12, the lighting element 32 carries supporting discs 33, 34, one at each end, the discs being of a size to fit snugly within the faceted tubing 35 which surrounds the lighting element, the discs having central openings 36, 37 respectively to fit snugly on the element 32. Such discs may be made of any desired material such as plastic, glass, metal, etc. Desirably they will be supplied with openings or perforations 28, 39 to permit air circulating and heat dissipation.

In the forms shown above, the faceting and splines have been shown as substantially straight ribs running longitudinally throughout the length of the tubing. In lieu of such straight ribs, the ribs may be given other configurations as for example they may take the form of helical convolutions which are readily formed during extrusion. Such form is illustrated in section in Figure 13 where the extruded tubing 40 carries faceting ribs ll, 4| in the form of helices internally of the tubing. Here too, the ribs may be in the nature of serrations with angles of 60, although other forms and angles may be used. Such tubing with helical convolutions of facetin ribs may be used in any of the manners set forth above, for lighting fixtures, either with or without splines, for containers and in divers other ways.

Faceting ribs as shown above are most desirably employed on the internal surfaces of the tubing. Less preferably they may be formed on the outer surfaces of the tubin either as straight longitudinal ribs or in the form of convolutions. This is shown in Figure 14 in section through the tubing 52 which carries the external longitudinal serrations or ribs 43, tubing of this character being produced by extrusion from any desired plastic or resin as set forth above. It may be used for lighting fixtures, for container, etc. as explained above for other forms of tubing, and may be dyed internally or surface washed for dyein effects. For many reasons however the internally faceted tubing is more desirable.

The lighting effects obtained by the splined or faceted tubing of the present invention is noteworthy. When viewed from any fixed position, the light is diffused and transmitted through walls of varying angular relationship to the observer so that a varying pattern and shaded effect is obtained that is most pleasing but more importantly very effective in removing glare without sacrifice of essential lighting. Further when splines are present as well as faceting, the splines produce a different light transmission effect than do the facets or ribs, again giving a pattern of variegated effect. The lighting effects thus obtained which vary with transmitted and reflected light, are very striking, making the tubin very desirable when used as set forth herein for lighting elements, and most effective in giving new types of artistic effects in containers.

The thermoplastic employed for the present invention should be at least translucent where light diffusion is an end sought either for lighting fixtures or containers. The extent of light transmission can be utilized in conjunction with splines and/or faceting ribs to vary the effect obtained. While, therefore, transparent or translucent plastics, clear or dyed, will generally -be employed; in some cases where the fluting and/0r faceting is on the outside of the tubing, opaque or semi-opaque material can be used.

This application is a continuation-in-part of application 563,764, filed November 16, 1944, now abandoned.

Having thus set forth my invention, I claim:

1. A light-transmitting-thermoplastic tube of discrete length to encircle an elongated lighting element, said tube having a number of splines extending in symmetrical relation from the inner wall of the tubing internally thereof for a substantial distance, the internal diameter of the tube being such that the height of the splines will position the lighting element within the tube and spaced therefrom throughout its periphery to provide substantially uniform heat dissipation about the tube.

2. A continuous length of extruded lighttransmitting-thermoplastic tubing of a size to encircle an elongated lighting element, said tubing having a number of splines extending in symmetrical relation from the inner wall of the tubing internally thereof for a substantial distance, the splines and tubing being integral, the internal diameter of the tubing being such that the height of the splines will position the lighting element within the tubing and spaced therefrom throughout its periphery to provide substantially uniform heat dissipation about the tubing.

3. Tubing as set forth in claim 2 in which the splines are radial.

4. Tubing as set forth in claim 2 in which the splines are angularly disposed.

5. A tube as set forth in claim 1, at least some of the walls of the tube between the splines being provided with serrated faceting to effect light diffusion.

6. Tubing as set forth in claim 2, at least some of the inner walls of the tubing between the splines being provided with serrated faceting to effect light diffusion.

'7. Tubing as set forth in claim 2, at least some of the inner Walls of the tubing between the splines being provided with faceting to effect light diffusion, the surfaces of the splines and the inner walls of the tubing being dyed with a light transmitting dye.

8. A light-transmitting-thermoplastic tube of discrete length to encircle an elongated lighting element, said tube having a number of splines extending in symmetrical relation from the inner wall of the tube internally thereof for a substantial distance, the splines and tube being integral, the internal diameter of the tube being such that the height of the splines will position the lighting element within the tube and spaced therefrom throughout its periphery to provide substantially uniform heat dissipation around the tube, the internal wall of the tube carrying integral serrated faceting triangular ribs at 60 angles between the splines to produce light diffusion.

CHARLES E. SLAUGHTER.

(References on following page) 9 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Schmitz Feb. 27, 1906 Wittstein June 20, 1933 Number 10 Name Date Clark et a1 Oct. 3, 1933 Guth Mar. 24, 1942 Larchar Apr. 27, 1943 Dreyfuss May 25, 1943 Roberts Jan. 2, 1945 Harrison Nov. 20, 1945 

